1. Field of the Invention
In general, the present invention relates to air conditioning systems used in aircraft. More particularly, the present invention relates to after market air conditioning systems that are used to upgrade and replace air conditioning systems that had been manufactured for installation in aircraft.
2. Prior Art Description
The present invention relates to private aircraft or small commercial aircraft that have turbine (turboprop or jet) or piston engines. Examples of such aircraft would be the King Air Aircraft manufactured by Beechcraft Corporation of Wichita, Kans. Many such aircraft have air conditioning units that are powered by the engines of the aircraft. For example, the King Air series 200 & 300 aircraft are twin-engine aircraft that have their air conditioning units run by the right engine on the aircraft.
The problems associated with having an air conditioning unit powered by an aircraft engine are self-evident. That is, the engine of the aircraft must be running in order for the air conditioning unit to function. Accordingly, if the aircraft is just sitting on the tarmac of an airport on a hot day, the right engine must be kept running in order to keep the cabin cool. This involves issues of noise, expensive aircraft fuel, safety, and additional maintenance.
Aircraft engines do not operate at their highest efficiency when running at idle. Consequently, an aircraft owner can expend a significant amount of fuel just running the engines for air conditioning purposes. Furthermore, aircraft engines require maintenance after surpassing a certain number of operating hours. Thus, aircraft that run at idle just to provide air conditioning require maintenance more often than aircraft that are not run at idle.
Many aircraft are manufactured with electric air conditioning systems. When such aircraft are parked on an airport tarmac, those aircraft can be powered by means of an external electrical extension cord while the aircraft engines are shut off. However, typical aircraft air conditioners require over 100 amperes of 28-volt direct current power. This requires the use of a converter that can convert the incoming alternating current to the required direct current. Even higher amperage is drawn in the initial starting stages of the air conditioning systems. As such, simply connecting an extension cord is not a solution since such amperages surpass the capacity of small diameter extension cords and the power circuits they are plugged into. Rather, to provide power to an aircraft on the tarmac, often a motorized generator must be provided or a large voltage conditioner must be used that is connected to a high power line source through a heavy extension cord.
A need therefore exists for an economical system that enables an airplane with an engine powered air conditioning system to be converted into an airplane with an electrical air conditioning system. A need also exists for a variable power air conditioner system that can be operated at reduced current levels from conventional 120-volt power outlets. Yet a further need exists for an air conditioning system for an aircraft that has a “soft-start” means so that high starting current requirements are eliminated. Furthermore, a need exists for compact power converter installed right on the aircraft that transforms ordinary alternating house power to 28-volt direct current aircraft power. In this manner only an extension cord is required to pre-cool the aircraft while it is sitting on the tarmac.
These needs are met by the present invention as described and claimed below.